The volunteer had been working with a small charity called Help Refugees, which works in northern French camps.

She was in New York at the time but alerted one of the charity's managers, Tanya Freedman, in the UK.

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A woman walks with her child in the Calais 'Jungle'

Freedman said: "Around about lunchtime they received a text message which roughly said, 'I'm in a truck, it's not stopping, I've got no oxygen ... help'.

"Because they were in New York and I was in London they rang me straight away and I got hold of Kent Police."

Using an interpreter the force spoke to the boy and the lorry was traced to Leicestershire.

Freedman said: "They broke in the back and got everybody out."

The child was among 15 people discovered by police in the vehicle at a service station on the M1.

He is thought to have stowed away in a lorry bound for the UK with his elder brother.

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The child was found at a service station on the M1

Leicestershire Police said it was called by a partner agency to Leicester Forest East service station just after 3pm on Thursday.

Fourteen people were arrested on suspicion of being illegal entrants to the UK. In addition, a man was arrested on suspicion of assisting illegal entry.

A spokeswoman for the force added: "Safeguarding measures were put in place for a child who was found in the truck."

The case is now being dealt with by immigration services.

Meanwhile, in another incident on Friday afternoon police were called to Toddington service station on the M1 following reports that 13 suspected illegal immigrants had been found in the back of a lorry.

Two have been taken to hospital, while the rest are being taken into custody.